How to Reduce Relay Noise in PLC Systems

Today we are going to discuss about Relay Noise reduction method. Sometimes we observe more noise is generating by relay output switching. In such case , a Noise filter must be connected to the load side or other appropriate countermeasures must be provided external to the PLC.

Countermeasures are not required if the frequency of load switching for the whole system with the PLC included is less than 5 times per minute means required after more than 5 times per minute.

Countermeasure Example

When switching an inductive load,connect an surge protector,diodes,etc in parallel with the load or contact as shown below:

When switching a load with a high inrush current such as an incandescent lamp, Suppress the inrush current as shown below: